Crunchy fish gratin recipe

Name: Crunchy fish gratin
Yield: Serves 6
Ingredients: 2 x 240g bags baby spinach, wilted; 280g boneless haddock fillets, skinned and cut into even chunks; 2 smoked mackerel fillets, skinned and torn into chunks; 1 x 150g pack cooked and peeled king prawns; 150g half-fat crème fraîche; 50g fat-free fromage frais; 1 tsp Dijon mustard; 1 lemon, zested; 2 tbsp chopped flat-leaf parsley; 3 spring onions, chopped; 2 tomatoes, sliced; 30g porridge oats with oatbran and wheatbran; 10g cornflakes; 30g Cheddar, grated (optional); 2 tbsp toasted three-seed mix; boiled potatoes, to serve

This crunchy fish gratin not only makes a quick and delicious weeknight supper but it’s healthy too. Topped with a combination of oats, cornflakes and three-seed mix, this easy dish is ideal for feeding a crowd. Use any combination of seafood that's available.

See method

Serves 6
5 mins to prepare and 25 mins to cook
273 calories / serving

Healthy

Shop your ingredients

Tesco Baby Spinach 250G
2 x 240g bags baby spinach, wilted
£1.30
£5.20/kg
Tesco Boneless Haddock Fillets 280G
280g boneless haddock fillets, skinned and cut into even chunks
£5.85
£20.89/kg
Tesco Peppered Smoked Mackerel Fillets
2 smoked mackerel fillets, skinned and torn into chunks
£5.63
£25.00/kg
Tesco Cooked And Peeled King Prawns 150G
£3.00 Clubcard Price
(£20.00/kg)
Offer valid for delivery from 16/09/2026 until 06/10/2026
1 x 150g pack cooked and peeled king prawns
£3.50
£23.33/kg
Tesco 50% Less Fat Creme Fraiche 300Ml
Aldi Price Match
150g half-fat crème fraîche
£0.75
£2.50/litre
Creamfields Apricot Strawberry Raspberry Fromage Frais 12 X 50G
Aldi Price Match
50g fat-free fromage frais
£0.85
£1.42/kg
Tesco Dijon Mustard 185G
Aldi Price Match
1 tsp Dijon mustard
£0.45
£2.43/kg
Tesco Lemons Each
1 lemon, zested
£0.37
£0.37/each
Tesco Fresh Cut Flat Leaf Parsley 30G
Aldi Price Match
2 tbsp chopped flat-leaf parsley
£0.50
£16.67/kg
Tesco Bunched Spring Onions 100G
49p Clubcard Price
(£4.90/kg)
Offer valid for delivery from 08/09/2026 until 05/10/2026
3 spring onions, chopped
£0.69
£6.90/kg
Tesco Classic Round Tomatoes 6 Pack
Aldi Price Match
2 tomatoes, sliced
£0.99
£0.16/each
Grower's Harvest Porridge Oats 1Kg
Aldi Price Match
30g porridge oats with oatbran and wheatbran
£0.85
£0.85/kg
Tesco Corn Flakes 500g
Aldi Price Match
10g cornflakes
£0.95
£1.90/kg
Creamfields Mature Grated Cheddar 250g
Aldi Price Match
30g Cheddar, grated (optional)
£1.89
£7.56/kg
Tesco Toasted 3 Seed Mix 300G
Any 4 for 3 Clubcard Price - Cheapest Product Free - Selected Dried Fruit Nuts And Seeds
Offer valid for delivery from 30/09/2026 until 26/10/2026
This product's currently out of stock
2 tbsp toasted three-seed mix
Tesco All Rounder Potatoes 2Kg
Aldi Price Match
boiled potatoes, to serve
£1.32
£0.66/kg

Method

Preheat the oven to gas 6, 200°C, fan 180°C. Arrange the wilted spinach, fish and prawns in a roasting tin. Mix together the crème fraîche, fromage frais, mustard, lemon zest, most of the chopped parsley and spring onions. Season, spoon over the fish and top with the tomato.
Mix together the oats, cornflakes, cheese, seeds, reserved parsley and remaining spring onions, then scatter over the fish. Bake for 20-25 mins, until golden and cooked through. Serve with boiled potatoes alongside.